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Sponsoring members of NACE International, NACE Foundation
QMF-570
104-254
P
RODUCT
I
NSTRUCTIONS
MODEL CPV- 4 VOLTMETER
IMPORTANT NOTE: Do not use this instrument in an explosive environment.
The Model CPV-4 Digital Cathodic Protection Voltmeter is used for measuring D.C. potentials between a
reference electrode and a structure.
1. UNPACKING
Check all components against packing list. If damage has occurred in shipment, file a claim with the carrier
immediately. If it is necessary to contact your supplier or the manufacturer concerning damaged or missing items,
be sure to include all the information, such as serial number, purchase order number, and invoice number. This
will assure you of obtaining proper and expeditious service.
2. PREPARATION OF HALF-CELL
Please note that in most cases the half-cell is shipped dry, and must be properly charged with distilled water
before operation.
3. OPERATION WITH HALF-CELL ELECTRODE ATTACHED
A. Remove protective vinyl cover from end of half-cell electrode.
B. Place ceramic end of half-cell in contact with moist earth.
C. Connect test lead from negative terminal on instrument to the structure.
D. Observe and record meter reading. Note: No switch to push for taking reading once the voltmeter has been
turned on.
4. DIFFERENCES BETWEEN METHODS OF CONNECTION
The Model CPV-4 has a connection for the half-cell to screw into the back of the voltmeter. When using this
option, the half-cell is connected to the Positive (+) side of the voltmeter. A test lead is then connected between
the Negative (-) post of the voltmeter and the structure.
This setup is used by many companies and technicians, as a "good" read, for instance 0.85v, is displayed as a
positive number. Many companies and technicians like to use positive numbers in recording reads. Also, an
analog meter may not display a negative reading, so companies or technicians who have both digital and analog
meters have standardized using this method.
However, there are some groups that teach a different connection method. NACE International and Peabody's
Control of Pipeline Corrosion, for example, both suggest connecting the Negative (-) terminal to the half-cell, and
the Positive (+) to the structure. This would then change the polarity of the reading, so that the same reading as
given in the previous example would then be displayed as -0.85v.
To connect the Model CPV-4 CP Voltmeter using the NACE / Peabody method, do not screw the half-cell into the
voltmeter. Use both lead cables provided, connecting the Red (+) cable between the structure and the Positive (+)
terminal on the voltmeter, and the Black (-) cable between the half cell and the Negative (-) terminal on the
voltmeter.
